题目

    When I first heard about geocaching（地理寻宝），I was skeptical．But the more I thought about it, the more it seemed like an interesting idea．I at least wanted to try it once．     Having familiarized myself with how the game works, I set out in search of my first cache．My trip took me through a series of lively hutong（胡同）,past a number of small temples, and right into the courtyard of a quiet youth hotel．I spent several minutes looking around, but couldn't find anything．Just before l was about to give up,I spotted a colorful object in the crack of （2008?通州区二模）对下列自然现象解释正确的是（　　）A．形成“露”是熔化现象B．形成“白气”是液化现象C．形成“雾”是汽化现象D．形成“霜”是升华现象